1. Technical Field
The present invention relates to the technical field of liquid crystal devices. In particular, the present invention relates to a structure of a liquid crystal device which can change a display mode between a reflective mode and a transmissive mode, and to an electronic device using the liquid crystal device.
2. Background Art
Reflective liquid crystal devices consuming small amounts of electrical power have been widely used in portable devices and display sections in various apparatuses. Since, however, the display is performed by external light, an image is not visible in dark environments. Thus, some proposed liquid crystal devices use external light in a lighted environment as in general reflective liquid crystal devices, and an internal light source in dark environments so as to maintain a visible state. As disclosed in Japanese Patent Application Laid-Open Nos. 57-049271, 57-049271, and 57-049271, each device has a polarizer, a transflector, and a backlight, in that order, at the outer face, away from the viewer, in a liquid crystal panel. The liquid crystal device performs reflective display using external light reflected by the transflector in a lighted environment, and transmissive display using light from the backlight, which is turned on so as to maintain a visible state, transmitted through the transflector in dark environments.
Another liquid crystal device having improved brightness in a reflective display mode is disclosed in Japanese Patent Application Laid-Open No. 8-292413. The liquid crystal device has a transflector, a polarizer, and a backlight, in that order, at the outer face, away from the viewer, of the liquid crystal panel. The device performs reflective display using external light reflected by the transflector when the environment is light, and transmissive display using light from the backlight, which is turned on so as to maintain a visible state, transmitted through the polarizer and the transflector. Since the polarizer is not provided between the liquid crystal cell and the transflector, brighter display is achieved in a reflective mode compared to the above-mentioned liquid crystal devices.
In the liquid crystal device disclosed in Japanese Patent Application Laid-Open No. 8-292413, however, a transparent substrate is disposed between a liquid crystal layer and the transflector; hence, problems, such as double imaging and blurred imaging, occur.
Color liquid crystal display has been required with recent development of portable devices and office automation devices. Apparatuses using reflective liquid crystal devices also require color display. In a combination of the liquid crystal device disclosed in the above patent application with a color filter, the transfiector is arranged behind the liquid crystal panel. Thus, the thick transparent substrate lies between the liquid crystal layer with the color filter and the transflector, resulting in occurrence of double imaging or blurred imaging due to parallax and insufficient coloring.
In order to solve the problems, Japanese Patent Application Laid-Open No. 9-258219 discloses a reflective color liquid crystal device in which a reflector is disposed so as to come into contact with the liquid crystal layer. This liquid crystal device, however, cannot display visible images in dark environments.
In addition, Japanese Patent Application Laid-Open No. 7-318929 discloses a transflective liquid crystal device in which a pixel electrode functioning as a transflective film is provided on the inner face of the liquid crystal cell. Since this liquid crystal device has a transflective film such as a metallic thin film having fine defects including pinholes, dimples, and fine openings, an oblique electric field which is generated on the periphery of the defects and openings causes unsatisfactory orientation of the liquid crystal, producing many technical problems which inhibit high-quality image display. That is, a high contrast and brightness are not achieved, and coloring due to wavelength dispersion of light inevitably occurs both in a reflective display mode and a transmissive display mode. Furthermore, it is difficult to achieve both prevention of brightness defects at the gap between pixel electrodes or an improvement in contrast and an improvement in brightness in a reflective display mode. Furthermore, the production process requires addition of a particular step; hence, the device satisfies with great difficulty a typical demand for reduction in production cost in this technical field.
The present invention has been accomplished in view of the above-mentioned problems and has an object to provide a transflective liquid crystal device, which is changeably used both in a reflective display mode and a transmissive display mode, does not produce double imaging blurred imaging due to parallax, and can display high-quality images, and to provide an electronic apparatus using the liquid crystal device.